In the Oto-Neurological Laboratory of the Baltimore City Hospitals clinical investigations are carried out on patients with cochlear and vestibular dysfunctions and a variety of pathological conditions involving different structures of the temporal bone. These investigations include an Otorhinolaryngological examination, cochlear and vestibular function studies, roentgenological investigations, and occasionally tests for aphasia. The medical, surgical, neurological and neurosurgical examinations are being performed by the respective services. At autopsy the temporal bones, and whenever indicated, the brains, are secured. The temporal bones are processed in the Temporal Bone Pathology Laboratory, the brains in the Neuro-Pathology Laboratory of the Traylor Research Building of the Johns Hopkins University School of Medicine. The objectives of this research are to correlate clinical and histopathological observations in an attempt to increase the knowledge about the poorly understood mechanisms of certain disease processes involving the cochlear and vestibular systems and other structures of the human temporal bone.